How did you prototype the board without knowing the answer?There is no AVR ICSP.Uses RS232 TTL RFduino programming using Arduino IDE.Otherwise low level is programmed using JTAG SWD pins. Check the documentation for nRF51822.

The USB programmer is just a USB to serial converter. It does not have a bootloader. The bootloader is built into the RFduino module. Have you found the documentation at RFduino.com? The JTAG SWD is only used if you want to blow away the RFduino/Arduino builtin bootloader and program at the lowest level.. which would be ARM Cortex M0.

I am not an employee of RFdigital. Just a community user who happens to be a moderator.

The bootloader firmware is programmed into the nRF51822 read protected flash by RFdigital. They keep secret the actual bootloading code and exactly where that loads into the nRF51822. So if you blow away their bootloader using JTAG/SWD to install your own ARM code or MBED, or Nordic libraries you won't be able to reload RFdigitals bootloader as they don' make that binary/hex available. I guess they figure if they made that available then everyone would install that on their hardware too and perhaps not buy their SOCs. That is why I say if you decide to go with installing MBED or Nordic firmware via JTAG you will loose all Arduino IDE, and SimbleeForMobile, for example, features.

The advantage of still using the Simblee SOC or the RFduino Module in your designs, if you go with custom low level programming, is that it is the best packaging of the nRF51822 and assorted bits and pieces.. like the crystals and antenna. If I was running the company I would be selling boocoo of the chips and not care what people put on it. The money is in the condensed complete system on chips. And make the firmware open source so the community can fix and improves things mucho faster. And make the chips so cheap no one would want to waste their time designing in the nRF and support components on their own.

If that is true then I'm with you 99%. Just give the board serial I/O and burn the code in from the Arduino IDE.

So one more question: What does all this ancillary circuitry do in the above SF board? Taking signals from the serial DTR pin? Thanks

Yes, the Simblee SOC is bought from RFdigital and mounted on the sparkfun board. Sparkfun has really good documentation on how things work.

The schematic you show is a manual reset button in conjunction with the DTR through a capacitor. The DTR line is used to by the Arduino IDE to reset the Simblee/RFduino to tell the bootloader to go into programming mode or run mode.

Yes, the Simblee SOC is bought from RFdigital and mounted on the sparkfun board. Sparkfun has really good documentation on how things work.

The schematic you show is a manual reset button in conjunction with the DTR through a capacitor. The DTR line is used to by the Arduino IDE to reset the Simblee/RFduino to tell the bootloader to go into programming mode or run mode.

OK so here is my summary:

1. RF Digital puts the boot loader in all chips as part of the manufacturing process2. Most designs can just use the serial port to load firmware into the Simblee3. The RESET circuit should have a differentiator circuit like the one above to go between prog mode and run mode using DTR4. The firmware is protected by default because there is no way to read it out

Another set of facts is the Simblee is FCC, CE, RED and bunch of others approved. If you change any firmware etc, it no longer is a Simblee device.UL and FCC and others would want to retest the device.At my work, I have used Teensy devices with software to interface with Medical devices. If I change the software enough, I would need to send out the system for a retest of over $15,000. That will not happen, so I do a little change that simply lites an LED or not.Current devices now on the Simblee has been qualified for UL/FCC/FDA of our foot switch wireless upgrade. In fact, the resolve of the only one failure was easy and was easier than our 2 previous models.